perf(hooks,tools): optimize string operations and reduce redundant iterations

- output-renderer, hashline-edit-diff: replace str += with array join (H2)
- auto-slash-command: single-pass Map grouping instead of 6x filter (M1)
- comment-checker: hoist Zod schema to module scope (M2)
- session-last-agent: reverse iterate sorted array instead of sort+reverse (L2)

src/hooks/auto-slash-command/executor.ts

@@ -44,12 +44,6 @@ export interface ExecutorOptions {
   agent?: string
 }
 
-function filterDiscoveredCommandsByScope(
-  commands: DiscoveredCommandInfo[],
-  scope: DiscoveredCommandInfo["scope"],
-): DiscoveredCommandInfo[] {
-  return commands.filter(command => command.scope === scope)
-}
 
 async function discoverAllCommands(options?: ExecutorOptions): Promise<CommandInfo[]> {
   const discoveredCommands = discoverCommandsSync(process.cwd(), {
@@ -60,14 +54,18 @@ async function discoverAllCommands(options?: ExecutorOptions): Promise<CommandIn
   const skills = options?.skills ?? await discoverAllSkills()
   const skillCommands = skills.map(skillToCommandInfo)
 
+  const scopeOrder: DiscoveredCommandInfo["scope"][] = ["project", "user", "opencode-project", "opencode", "builtin", "plugin"]
+  const grouped = new Map<string, DiscoveredCommandInfo[]>()
+  for (const cmd of discoveredCommands) {
+    const list = grouped.get(cmd.scope) ?? []
+    list.push(cmd)
+    grouped.set(cmd.scope, list)
+  }
+  const orderedCommands = scopeOrder.flatMap((scope) => grouped.get(scope) ?? [])
+
   return [
     ...skillCommands,
-    ...filterDiscoveredCommandsByScope(discoveredCommands, "project"),
-    ...filterDiscoveredCommandsByScope(discoveredCommands, "user"),
-    ...filterDiscoveredCommandsByScope(discoveredCommands, "opencode-project"),
-    ...filterDiscoveredCommandsByScope(discoveredCommands, "opencode"),
-    ...filterDiscoveredCommandsByScope(discoveredCommands, "builtin"),
-    ...filterDiscoveredCommandsByScope(discoveredCommands, "plugin"),
+    ...orderedCommands,
   ]
 }